1. Technical Field of the Invention
The present invention relates to information signal coding schemes in general and, in particular, to coding schemes suitable for single media or multimedia signal coding, such as video coding or audio coding.
2. Description of the Prior Art
The MPEG-2 video coding standard, which was developed about 10 years ago primarily as an extension of prior MPEG-1 video capability with support of interlaced video coding, was an enabling technology for digital television systems worldwide. It is widely used for the transmission of standard definition (SD) and High Definition (HD) TV signals over satellite, cable, and terrestrial emission and the storage of high-quality SD video signals onto DVDs.
However, an increasing number of services and growing popularity of high definition TV are creating greater needs for higher coding efficiency. Moreover, other transmission media such as Cable Modem, xDSL or UMTS offer much lower data rates than broadcast channels, and enhanced coding efficiency can enable the transmission of more video channels or higher quality video representations within existing digital transmission capacities.
Video coding for telecommunication applications has evolved through the development of the MPEG-2 coding standard, and has diversified from ISDN and Tl/El service to embrace PSTN, mobile wireless networks, and LAN/Internet network delivery. Despite this evolution, there is still a need to maximize coding efficiency while dealing with the diversification of network types and their characteristic formatting and loss/error robustness requirements.
Recently, the MPEG-4 Visual standard has also begun to emerge in use in some application domains of the prior coding standards. It has provided video shape coding capability, and has similarly worked toward broadening the range of environments for digital video use.
However, the video schemes available today have in common, that it is difficult to adapt an already coded video stream during its way from its creation to the arrival at a receiver in order, for example, to adapt the performance level of the coded video stream to the performance of the receiver or to the performance of the transmission link connecting the coded video streams source and the receiver.
For example, a MPEG-4 data stream may be provided at a video server in Dolby surround, thus providing a relatively large number of audio channels. However, the receiver may be a device capable of only reproducing mono-audio information. In this case, transferring the video-coded stream with full performance level, i.e. incorporating all audio channels, would mean waste of transfer-linked capacity. Thus, it would be advantageous if a gateway between the coded video stream source and the receiver could convert the coded video stream from its initial performance level to a lower performance level. However, in available video coding schemes, the gateway may not convert a video data stream from a higher performance level to a lower performance level merely by discarding the portion of the coded video data stream pertaining the excessive channels without manipulating the remainder of the coded video stream, i.e. the portion concerning both the higher performance level as well as the lower performance level.
Therefore, there is a need for a video coding scheme, which allows a higher “network friendliness” to enable simple and effective customization for a broad variety of systems. To be more specific, the video coding scheme should allow a greater customization of carrying the video content in a manner appropriate for each specific network. Moreover, the customization and adaptation of coded video streams should be possible with reasonable efforts.